Scala concepts: Pattern Matching

Pattern matching in Scala lets you quickly identify what you are looking for in a data, and also extract it.

assert("Hello World".collect {
  case character if Character.isUpperCase(character) => character.toLower
} == "hw")

assert("Hello World".filter(Character.isUpperCase).map(_.toLower) == "hw")

assert((1 to 10).collect {
  case num if num % 3 == 0 => "Fizz"
  case num if num % 5 == 0 => "Buzz"
}.toList == List("Fizz", "Buzz", "Fizz", "Fizz", "Buzz"))

Pattern matching is used by methods like Collect, but can also be easily integrated into normal functions.

Pattern matches are effectively "Partial Functions", of type PartialFunction[Input, Output] which is isomorphic to Input => Option[Output]. See Option Type.